This paper is concerned with the microstructure observed in colloidal dispe
rsions of charged polymeric particles and their interaction potential at ve
ry low ionic strength. Both aspects are probed with the aid of new experime
ntal data for nonaqueous media. The structure factor of ordered dispersions
(with methanol-water and ethanol-water solvent mixtures) was determined us
ing static light scattering. A different behavior (in the studied range of
molar fraction) depending on the alcohol type is found. These results are a
nalyzed assuming a Yukawa potential and applying integral equation theories
(the Ornstein-Zernike equation and the HNC closure). The obtained effectiv
e charge is almost constant for methanol-water mixtures, whereas a decrease
with the alcohol molar fraction is observed for ethanol-water. In order to
account for these effects, a charge renormalization procedure is applied a
nd discussed. The surface charge turns out to be an unsuitable input parame
ter for such an approach. (C) 1999 American Institute of Physics. [S0021-96
06(99)51212-9].